Magnetic stiffness reduction for audio transducers

Abstract

Aspects of the subject technology relate to stiffness reduction for audio transducers, such as speakers. Stiffness reduction can be provided using one or more magnetic structures configured to move with a voice coil and/or a diaphragm of the speaker, and assist in the motion of the voice coil and/or diaphragm via magnetic interaction with one or more magnets of the speaker. In one or more implementations, the one or more magnetic structures may form a tri-stable system with the one or more magnets.

What is claimed is: 
     
         1 . An electronic device comprising:
 audio transducer, the audio transducer comprising:
 a first magnet; 
 a voice coil; 
 a sound-generating component that is mechanically coupled to one of the voice coil or the first magnet, and that is movably suspended with respect to the other of the voice coil or the first magnet; and 
 one or more magnetic structures mechanically coupled to the voice coil and configured to magnetically interact with the first magnet to provide a tri-stable positioning of the sound-generating component. 
   
     
     
         2 . The electronic device of  claim 1 , the audio transducer further comprising a sealed back volume comprising air that generates a stiffness that resists motion of the sound-generating component, and wherein the tri-stable positioning of the sound-generating component provides a negative stiffness that effectively cancels at least some of the stiffness generated by the air in the sealed back volume. 
     
     
         3 . The electronic device of  claim 1 , wherein the one or more magnetic structures comprise a first magnetic structure adjacent to a first end of the voice coil and a second magnetic structure adjacent to a second end of the voice coil. 
     
     
         4 . The electronic device of  claim 3 , wherein the first magnetic structure comprises a first ring of magnetic material attached to a voice coil former at a first location that is adjacent to the first end of the voice coil, and wherein the second magnetic structure comprises a second ring of magnetic material attached to the voice coil former at a second location that is adjacent to the second end of the voice coil. 
     
     
         5 . The electronic device of  claim 3 , wherein the one or more magnetic structures further comprise a third magnetic structure disposed between the first magnetic structure and the second magnetic structure and between first and second portions of the voice coil. 
     
     
         6 . The electronic device of  claim 5 , wherein the third magnetic structure comprises a ring of magnetic material attached to a voice coil former between the first and second portions of the voice coil. 
     
     
         7 . The electronic device of  claim 1 , wherein the one or more magnetic structures comprise one or more sections of the voice coil that are formed from a magnetic material. 
     
     
         8 . The electronic device of  claim 1 , wherein at least one of the one or more magnetic structures comprise a shape configured to progressively interact with the first magnet in response to a progressively changing distance from the first magnet. 
     
     
         9 . The electronic device of  claim 1 , wherein at least one of the one or more magnetic structures comprises a magnetic portion of a voice coil former on which the voice coil is formed. 
     
     
         10 . The electronic device of  claim 1 , wherein the first magnet comprises a pair of magnet portions separated by a gap. 
     
     
         11 . The electronic device of  claim 1 , wherein the first magnet comprises a fixed magnet, wherein the voice coil is movably suspended with respect to the fixed magnet, wherein the sound-generating component is mechanically coupled to the voice coil, and wherein the one or more magnetic structures are configured to move with the voice coil. 
     
     
         12 . The electronic device of  claim 1 , wherein the first magnet comprises a first movable magnet, wherein the voice coil is a fixed voice coil, wherein the first movable magnet is movably suspended with respect to the fixed voice coil, wherein the sound-generating component is mechanically coupled to the first movable magnet, and wherein the one or more magnetic structures are fixed in position with the fixed voice coil. 
     
     
         13 . The electronic device of  claim 12 , wherein the first movable magnet is disposed on a first side of the voice coil, and wherein the audio transducer further comprises a second movable magnet on a second side of the voice coil. 
     
     
         14 . The electronic device of  claim 13 , wherein the audio transducer further comprises:
 an additional fixed voice coil between the first movable magnet and the second movable magnet; and   a third movable magnet between the fixed voice coil and the additional fixed voice coil.   
     
     
         15 . The electronic device of  claim 14 , further comprising a fixed magnet, wherein the second movable magnet is disposed between the fixed magnet and the additional fixed voice coil. 
     
     
         16 . An audio transducer, comprising:
 a first magnet;   a voice coil;   a sound-generating component that is mechanically coupled to one of the voice coil or the first magnet, and that is movably suspended with respect to the other of the voice coil or the first magnet; and   one or more magnetic structures mechanically coupled to the voice coil and configured to magnetically interact with the first magnet to provide a tri-stable positioning of the sound- generating component.   
     
     
         17 . The audio transducer of  claim 16 , further comprising a sealed back volume comprising air that generates a stiffness that resists motion of the sound-generating component, and wherein the tri-stable positioning of the sound-generating component provides a negative stiffness that effectively cancels at least some of the stiffness generated by the air in the sealed back volume. 
     
     
         18 . The audio transducer of  claim 16 , wherein the one or more magnetic structures comprise a first magnetic structure adjacent to a first end of the voice coil and a second magnetic structure adjacent to a second end of the voice coil. 
     
     
         19 . The audio transducer of  claim 18 , wherein the first magnetic structure comprises a first ring of magnetic material attached to a voice coil former at a first location that is adjacent to the first end of the voice coil, and wherein the second magnetic structure comprises a second ring of magnetic material attached to the voice coil former at a second location that is adjacent to the second end of the voice coil. 
     
     
         20 . The audio transducer of  claim 18 , wherein the one or more magnetic structures further comprise a third magnetic structure disposed between the first magnetic structure and the second magnetic structure and between first and second portions of the voice coil. 
     
     
         21 . The audio transducer of  claim 20 , wherein the third magnetic structure comprises a ring of magnetic material attached to a voice coil former between the first and second portions of the voice coil. 
     
     
         22 . The audio transducer of  claim 16 , wherein the one or more magnetic structures comprise one or more sections of the voice coil that are formed from a magnetic material. 
     
     
         23 . The audio transducer of  claim 16 , wherein at least one of the one or more magnetic structures comprise a shape configured to progressively interact with the first magnet in response to a progressively changing distance from the first magnet. 
     
     
         24 . The audio transducer of  claim 16 , wherein at least one of the one or more magnetic structures comprises a magnetic portion of a voice coil former on which the voice coil is formed. 
     
     
         25 . The audio transducer of  claim 16 , wherein the first magnet comprises a pair of magnet portions separated by a gap. 
     
     
         26 . The audio transducer of  claim 16 , wherein the first magnet comprises a fixed magnet, wherein the voice coil is movably suspended with respect to the fixed magnet, wherein the sound-generating component is mechanically coupled to the voice coil, and wherein the one or more magnetic structures are configured to move with the voice coil. 
     
     
         27 . The audio transducer of  claim 16 , wherein the first magnet comprises a first movable magnet, wherein the voice coil is a fixed voice coil, wherein the first movable magnet is movably suspended with respect to the fixed voice coil, wherein the sound-generating component is mechanically coupled to the first movable magnet, and wherein the one or more magnetic structures are fixed in position with the fixed voice coil. 
     
     
         28 . The audio transducer of  claim 27 , wherein the first movable magnet is disposed on a first side of the voice coil, and wherein the audio transducer further comprises a second movable magnet on a second side of the voice coil. 
     
     
         29 . The audio transducer of  claim 28 , further comprising:
 an additional fixed voice coil between the first movable magnet and the second movable magnet; and   a third movable magnet between the fixed voice coil and the additional fixed voice coil.   
     
     
         30 . The audio transducer of  claim 29 , further comprising a fixed magnet, wherein the second movable magnet is disposed between the fixed magnet and the additional fixed voice coil.